A push belt for a continuously variable transmission is generally known. Usually, such a push belt comprises two endless, ribbon-like carriers shaped like a closed loop for carrying a relatively large number of transverse elements. The transverse elements are arranged along the entire circumference of the carriers, wherein, during operation, they are able to transmit forces which are related to a movement of the push belt. Both the carriers and the transverse elements are manufactured from metal.
In the following description of the transverse element, the directions as mentioned refer to the situation in which the transverse element is part of the push belt. A longitudinal direction of the transverse element corresponds to a circumferential direction of the push belt. A vertical transverse direction of the transverse element corresponds to a radial direction of the push belt. A horizontal transverse direction of the transverse element corresponds to a direction perpendicular to both the longitudinal direction and the vertical transverse direction.
The transverse element has a first main body surface and a second main body surface, which are extending substantially parallel with respect to each other, substantially perpendicular to the longitudinal direction. The two main body surfaces have substantially the same contour, but a relief that is provided in each of the main body surfaces is different. At least a portion of the first main body surface of the transverse element is destined to contact at least a portion of the second main body surface of an adjacent transverse element in the push belt, whereas at least a portion of the second main body surface of the transverse element is destined to contact at least a portion of the first main body surface of another adjacent transverse element in the push belt. A circumferential surface, which has a relatively small dimension in the longitudinal direction, is extending between the two main body surfaces.
Two portions of the circumferential surface of the transverse element are destined to function as support surfaces for supporting the carriers of a push belt. These support surfaces are extending at an equal level. Two other portions of the circumferential surface of the transverse element are destined to function as contact surfaces for realizing contact between the transverse element and pulley sheaves of a pulley of a continuously variable transmission. These contact surfaces are extending at an angle with respect to each other, wherein these contact surfaces are divergent in a direction towards the support surfaces. The terms “top” and “bottom” which are used in the following are related to the direction of divergence; this is defined as being from bottom to top.
In the vertical transverse direction, from bottom to top, the transverse element comprises successively a basic portion, a neck portion and a top portion, wherein, in the horizontal transverse direction, the dimensions of the neck portion are relatively small. The basic portion comprises the support surfaces and the contact surfaces. In the push belt, the basic portion is located at the side of the inner circumference of the push belt, whereas the top portion is located at the side of the outer circumference of the push belt.
In one of the main body surfaces of the transverse element, a convex zone is located, which will hereinafter be referred to as tilting zone. This zone is extending along an entire width of the transverse element, and forms an even and round transition between two planar areas of the main body surface, which are located above each other in the vertical transverse direction. Usually, the tilting zone is located in a top part of the basic portion. An important function of the tilting zone is guaranteeing mutual contact between adjacent transverse elements which are located between the pulley sheaves of a pulley during operation of the push belt, and which are performing a tilting movement with respect to each other. By maintaining contact along a defined line, it is achieved that the forces which are related to a movement of the push belt are transmitted between adjacent transverse elements in a controlled fashion, under all circumstances.
According to the state of the art, the tilting zone is formed in the main body surface of the transverse element by clamping the transverse element or a piece of basic material from which the transverse element is manufactured between two tool elements, wherein a surface of one of the tool parts has a concave portion, as a negative of the convex tilting zone to be formed. When the tool elements having the transverse element positioned between them are moved towards each other under the influence of pressure, a displacement of material over a main body surface of the transverse elements, which is located at the side of the tool element having the concave portion, is being forced. It is especially achieved that material flows into a space that, in a first instance, is offered by the concave portion of the surface of the tool element. In this way, the convex zone is obtained on the main body surface of the transverse element.
The conventional method for forming the tilting zone in the main body surface of the transverse element has a number of disadvantages. In the first place, it is a costly matter to manufacture a tool element having a surface with an accurately defined concave portion. In the second place, the pressing forces which are needed to move the tool elements having the transverse element positioned between them towards each other are relatively high, as a consequence of which a relatively heavy construction is needed. In practice, there is a considerable risk that a required level of the pressing forces is not reached, and that the shape of the concave portion of the surface of the transverse element is not exactly taken up in the main body surface of the transverse element, as a consequence of which the shape of the eventually obtained tilting zone deviates from a defined shape.